There is a virus in your pc 100%.Please scan your pc.I am sure you will get benefit from this.

No man! There was no virus, this was because of CHINA FAKE PEN DRIVES, which are typically available at some markets at rupees 250 only ($5)! Now think, if someone gives you a 32GB pen drive at a cost of $5 in place of $35 - $36, what will happen to its quality!
Any way, thanks for your suggestion...